Champasak province in the context of Wat Phu

The Emerald Triangle is the shared border region between Cambodia, Laos and Thailand. It includes the area of Chong Bok (Thai: ช่องบก), a mountain pass through the Dangrek Range, which forms much of the natural boundary between Thailand and Cambodia. In Cambodia, the area is known as Mom Bei (Khmer: មុំបី).

The Emerald Triangle name was coined in 2000 as a project for international cooperation to promote tourism and economic development in the area. The name, referring to the area's lush environment, is a play on the pre-existing Golden Triangle region between Laos, Thailand and Myanmar. In the broader sense, the Emerald Triangle covers areas in seven provinces among the three countries: Preah Vihear, Oddar Meanchey and Stung Treng in Cambodia, Salavan and Champasak in Laos, and Ubon Ratchathani and Sisaket in Thailand. In the narrow sense, it refers to the boundary tripoint between the three countries, which lies near the Chong Bok pass. The pass has an elevation of 330 metres (1,080 ft).

Ubon Ratchathani (Thai: อุบลราชธานี, pronounced [ʔù.bōn râːt.tɕʰā.tʰāː.nīː]; Northeastern Thai: อุบลราชธานี, pronounced [ʔǔ.bōn lâːt.sā.tʰa᷇ː.ni᷇ː]), often shortened to Ubon (อุบลฯ), is one of Thailand's seventy-six provinces. It lies in lower northeastern Thailand (also called Isan). Ubon is about 630 km (390 mi) from Bangkok. Neighboring provinces are (from west clockwise) Sisaket, Yasothon, and Amnat Charoen. To the north and east it borders Salavan and Champasak of Laos, to the south Preah Vihear of Cambodia.

Sekong (also sometimes Xekong, Lao: ເຊກອງ, pronounced [séː kɔ̀ːŋ]) is a province of Laos in the southeast of the country. It is the second smallest province in Laos, covering an area of 7,665 square kilometres (2,959 sq mi). It is bordered by Vietnam to the east, Attapeu province to the south, Salavan province to the north, and Champasak province to the west. Sekong has the smallest population (129,398 as of 2020) and the lowest population density of any province. It was created in 1984 by splitting Salavan province. It is the most diverse province in Laos with 14 ethnic groups. The Sekong River, which divides the province, flows in a southerly direction into Cambodia and is navigable. The Dakchung Plateau and Xe Xap National Biodiversity Conservation Area are among the areas under protection.